Driving home last night and the car in front of me repeatedly crosses the double yellow line when no traffic is oncoming, and is closer to the line than I would be when there is oncoming traffic. I flashed my highs once as a 'reality check' for someone I thought was either drunk or texting.

I follow them at a safe distance for over a mile, until the next traffic light. I did have thoughts of calling 911, but before the light (I was going straight) the driver seemingly as an afterthought crosses 2 lanes (without incident) and makes a 'late' right turn with a Yield.

I hope he did not cause problems later.

How do you think the cops would have received the 911 call (assuming I had the license plate and car make / color) to give them?

That's a tough one. If its really bad, I would call dispatch just for my own piece of mind (I don't want to think about them killing someone later). Also, there are so many bad/distracted drivers that you might need dispatch preset on your phone.